1. Field of the Invention
The present invention is related to a front opening unified pod (FOUP), and more particularly, to at least one of latch structure disposed in a FOUP.
2. Description of the Prior Art
The semiconductor process consists of multiple procedures or steps, during which wafers are to be placed in different locations or different machines, and therefore in the process, wafers need to be transported from one place to another and even stored for certain period of time as required by the process flow. Wherein, wafer cassettes function both as storage containers and transportation containers and need to be compatible with different types of transportation and carrying devices and thus play a very important role in the semiconductor process.
As shown in FIG. 1, in which is a conventional front opening unified pod (FOUP). The FOUP, usually formed by one-piece injection molding, has a container body A and the inner side of the container body A is disposed with a plurality of wafer supporting pieces B; the wafer supporting pieces B and the container body A can be formed by one-piece injection molding, or the container body A can be formed with a plurality of integrated sockets by one-piece injection molding and the wafer supporting pieces B are then snap-fitted into the integrated sockets.
However, as the size of wafers increases, to over 300 mm for example, the size of wafer containers also needs to be increased. Yet when a large-sized wafer container is formed with injection molding using polymer material, the stress induced by the polymer material may cause distortion of the container body during its formation and may further lead to distortion of integrated wafer supporting pieces or sockets formed by one-piece injection molding; since the wafer supporting pieces or sockets are symmetrically disposed on left and right sides (for wafers to be horizontally placed in the container), slight distortion may lead to tilted position of wafers and affect the process and may even cause cracks in wafers and thus result in serious losses.
The door is usually disposed with retaining components that co-operates with the wafer supporting pieces to secure wafers in the container body; however, retaining components are generally fixed to the door and when the wafers placed in the container body are large-sized ones, the vibration of wafers may be stronger while being carried due to its large size, and fixed retaining components may result in lack of cushioning that causes wafers in the wafer container to crack and thus severe losses.
Moreover, a conventional latch structure comprises complex mechanical structures, which are more susceptible to breakdown and also friction during the process of operation that leads to contamination of wafers.
In addition, OHT system is usually used for carrying wafer containers, and an OHT head C (as shown in FIG. 1) is usually disposed on top of wafer containers to facilitate the robot in gripping and lifting wafer containers to other process platforms. The conventional OHT head C is usually lock-fastened with a plurality of lock-fasteners disposed at its center.
Loaded with large-sized wafers, a large-sized FOUP weighs heavier than a conventional small-sized FOUP. As the conventional OHT head C is only lock-fastened to the FOUP with a plurality of lock-fasteners and has to sustain the weight of the large-sized FOUP and of wafers within, distortion and cracks of the upper side of the FOUP may occur easily, and the OHT head C may break loose from the large-sized FOUP, which may fall down and be damaged and thus lead to a larger cost loss.
Furthermore, as a large-sized FOUP is manually transported with its opening facing upward, when the FOUP is placed on a flat surface, weight of large-sized wafers in the FOUP may exert considerable impact when the FOUP and the surface are in contact and thus result in cracks or chipping of large-sized wafers in the FOUP.